This invention relates to a fuel filling system for gasoline tanks not having an inlet pipe, such as used on motorcycles, and applies particularly to those machines outfitted with a catalytic converter.
In order to minimize pollution of the atmosphere by internal combustion engines, catalytic converters have become standard emission control devices for automobilies. Since catalytic converters will be significantly impaired by the use of leaded gasoline, vehicles equipped with catalytic converters must have a gasoline tank with a filler inlet having a restriction that admits only a nozzle with a spout of smaller diameter used in dispensing unleaded fuel. In addition, the filler inlet must be designed so that it will not pass more than 700 cc of gasoline before operating the automatic shutoff mechanism triggered by the plugging of a vacuum port located within about 0.87 inches (2.2 cm) of the tip when the introduction of gasoline into the filler inlet is attempted with a standard nozzle having a diameter of 0.93 inches (2.36 cm).
To satisfy these requirements, inserts have been designed for filler inlets which provide a 0.840 inch diameter restriction (2.13 cm diameter) more than 0.87 inches (2.2 cm) into the inlet, and a valve downstream of the restriction. When the nozzle spout of an unleaded fuel dispenser head is inserted into the filler inlet through the restriction, the valve is pushed open by the nozzle to admit fuel into the tank at a rate of 8.+-.1 gallon/minute (30.4.+-.3.8 L). Since the spout of a standard nozzle cannot be inserted into the filler pipe through the restriction, the valve will remain closed. As a consequence, any attempt to introduce leaded fuel into the tank will cause fuel to back up and plug the vacuum port of the nozzle to shut off the nozzle. The only fuel dispensed will thus be restricted to that which the insert will hold between the valve and the vacuum hole on the nozzle, which can be designed to be less than 700 cc. U.S. Pat. Nos. 3,730,216 and 3,911,977 are representative of this type of insert for automobile filler pipes.
These prior-art inserts have been designed for fuel tanks having fill pipes so that the nozzle can be inserted well past the restriction and still fill the tank completely. The nozzle is not shut off until fuel backs up in the filler pipe to plug the vacuum port. In some machines requiring a filler insert, the prior-art inserts cannot be used because there is no inlet pipe; instead the filler inlet opens directly into the tank, which is usually quite shallow, such as in the case of motorcycles. If the nozzle spout were to be inserted past the filler inlet restriction as far as it will go, only a disconcerting fraction of fuel can be put into the tank before the automatic shutoff is actuated. Moreover, it is generally necessary to watch the fuel level rising to detect when it is very near the top, and this would not be possible with a small nozzle inserted into a restricted opening. What is required is a filler insert which not only allows the tank to be filled to very near the filler opening without being able to see inside the tank, but also satisfies the other requirements, namely a restriction that will allow only unleaded fuel nozzles to be inserted, and pass a maximum of 700 cc of gasoline before automatic shutoff when an attempt is made to fill the tank with a larger, leaded fuel nozzle.